The present invention relates to a fender serving as a shock absorber at the time when a ship comes alongside or moored at the pier.
A fender as a shock absorber is disposed at the pier to protect both the ship and pier from an impact or friction produced at the time when the ship comes alongside or moored at the pier of the harbor.
As shown in FIG. 4(a), a fender 40 comprises a top section 40 as a contact surface with a ship body, and a leg section 44 attached to both ends of the top section 42, and is fixed to a pier 50 by inserting a bolt 48 into a flange section 46 of the tips of the leg section 44. As shown in 4(b), this fender 40 protects the ship body by deforming the leg section 44 to reduce the impact at the time when the ship comes alongside the pier.
As the fender, a fender made of rubber has widely been used, heretofore. However, since a rubber material used in the fender has normally a large friction coefficient .mu. of not less than 1, when a ship body 52 comes into contact with the fender 40 diagonally (at the time when the ship comes in contact with the pier diagonally), an excess force is locally exerted and deformation of the fender 40 becomes non-uniform. As a result, not only is the desired shock absorbing performance not exerted, but also the fender 40 itself is liable to cause damage such as crack and the like.
Since the ship body always rolls by an influence of wave and wind while the ship is moored at the pier, a friction force is produced between the fender and ship body. Therefore, as shown in FIG. 6, a shear force is exerted on the fender 40 by friction with the ship body 52 and the fender is liable to be deteriorated, for example, damage such as crack and the like arise.
On the other hand, a fender obtained by forming a coating layer of a material such as polyurethane having a low friction coefficient .mu. on the surface of a fender body of rubber alone is known, but the adhesion between the coating layer and fender body is low and the coating layer is liable to be peeled off.
To solve the above problems, there has been suggested a method of dispersing a compressive force given at the time when the ship comes alongside at the pier or reducing a friction force given at the time when the ship is moored at the pier by providing a surface layer 54 of a resin having a small friction coefficient, such as ultra-high molecular weight polyethylene (friction coefficient .mu.=0.2) on the top section of the fender 56 to make the surface of the fender slippery, as shown in FIG. 7. According to this method, the surface layer 54 is fixed by inserting a bolt 48 into a metal plate 58 embedded in the fender 56.
However, since the friction coefficient of the surface layer 54 is low, a friction force between the bolt 48 or washer 49 and the surface layer 54 is small. When the above-described excess force or shear force is exerted at the time when the ship comes alongside or is moored at the pier, the surface layer 54 is removed from the bolt 48 section, as shown in FIG. 8.
According to the above method, since parts such as is surface layer 54, is metal plate 58 and a bolt are required, additionally, the production cost of the fender becomes higher. On the other hand, even if the surface layer 54 is directly bonded on the surface of the top section of the fender 56 without using the bolt, the bonding force between the surface layer 54 and rubber is low and the fender is considerably deteriorated.